Tool-Chip Thermocouple Technique
Here is the schematic of tool-chip thermocouple set-up:
Generally, only the average temperature at the tool/chip interface
can be obtained. Sometimes, a tool-work thermocouple was also used.
The calibration of the tool-chip thermocouple is shown as:
Some limitations of this methods are mainly:
The elimination of parasitic e.m.f.'s which could affect the thermocouple
The calibration of the thermocouple output.
Embedded Thermocouple Technique
The following is a typical embedded thermocouple setup:
Infrared Radiation Technique
The first use of this technique was reported by Schwerd who developed a
total Radiation Pyrometer for determining the temperature distribution
at the surfaces of tool and workpiece.
Several researchers attempted to access to chip/tool interface
by scanning through holes drilled either in the work or tool. Prins' pyrometer
arrangement is shown as follows:
Limitation of the above measurements is that there is considerable
interference of the contact zone which must influence the heat flow and
the resulting temperature of either the chip or tool surface.
Infrared Photography technique proposed by Boothroyd can obtain
a full temperature field in the chip and workpiece. A calibration strip,
which was electrocally heated from one end,was simply used to calculate
the real temperature. The following setup was used at that time:
Today, many disavantages of this technique are overcomed.
Metal Microstructure and Microhardness Variation Measurement
Under suitable cutting conditions, the metallographic method can be used
to determining the temperature gradients in high speed steel cutting tools.
The following picture is the etched rake face of tool used to cut nickel
in normal dry atmosphere at 46 m/min, 0.25 mm/rev feed for 30 seconds(After
E. F. Smart and E. M. Trent):
However, the microstructure, microhardness and other properties change
to some extent dependent on temperature and time.
Thermosensitive Painting Technique
Using the thermosensitive paints for estimating cutting temperature is
because that these paints change colors at different temperature.
Limitations are that there is a relatively long time lag for the
colors to change and that small changes in temperature are not easy to
Temper Color Technique
This technique is based on the fact that the temper colors of some metals
are different at different temperatures. And it wasn't widely used.